highlighted in the data presented in the current study, direct
evidence to support the previous findings was not found. This may
be explained due to the use of different promoters: the 35S in
previous study [9] vs. the maize ubiquitin promoter used in our
study. Although these two strong promoters can be interchangeably
used, there may be spatial expression differences that may directly
impact nhaA over-expression, ion regulation, and salt tolerance.
The nhaA gene as a Na+/H+ antiporter from E. coli is a wellstudied
sodium and lithium extrusion system in prokaryotes. It
may confer different functions to eukaryotes because of different
cellular structures and function mechanisms. In S. cerevisiae, nhaA
is minimally present in the plasma membrane and a major
component of internal membranes, which confers lithium tolerance
and slight sodium sensitivity [17]. The bacterial nhaA